1. Field of the Invention
One embodiment of this invention relates to an improvement of a mobile communication system. More specifically, the present invention relates to switching of cellular stations accompanying inter-zone movement of mobile terminals, namely, relates to handover (hand-off).
2. Description of the Related Art
The mobile communication system provided with a plurality of cellular stations and a plurality of mobile terminals. Each cellular station is a facility on a network side, and individually forms a wireless zone (area, or cell). In each area, the mobile terminal communicates with a cellular station forming the area. A mobile terminal moving to another area switches a communication partner from a cellular station in connection to a cellular station at a movement destination. This processing is referred to as a hand-off.
The hand-off includes processing at an interface (wired resource) between the cellular station and the network, and processing at an interface (wireless resource) between the mobile terminal and the cellular station. Since any processing needs a certain extent of time, if the frequency of the hand-off increases, there is possibility that the processing will be behind time. For instance, before completion of the hand-off to the cellular station to be connected, the mobile terminal may move to the area of the further next cellular station. As the moving speed of the mobile terminal becomes faster, such a case is apt to occur. This situation is especially remarkable in a system of a micro cell system with a small cell radius. In such a case, since there is a risk that communication is disabled, it is forced to take prompt measures.
A technique to solve this kind of problem is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-268619. In this reference technique, the mobile terminal specifies the cellular station at the next hand-off destination on the basis of the previous hand-off record. After receiving the request from the mobile terminal, the network starts a hand-off process at the wired resource and the wireless resource. Therefore, the processing on the network side regarding the hand-off may be one step behind. If it is able to predict the cellular station of the hand-off destination on the network side, since a necessary process may be completed in advance, there is a possibility to further shorten the time required for the hand-off. However, such a technique has not been developed.